Chemical Mechanical Planarization (CMP) is a widely-used processing technique in the manufacturing of submicron technology integrated circuits (ICs). With ever-decreasing lithographic depth of focus as technology nodes shrink, planarity of the semiconductor wafer working surface has become a necessity. CMP is a polishing/material-removal process in which a polishing pad and a polishing slurry are used. The polishing slurry is often corrosive. Due to glazing, the material removal efficiency of polishing pads usually declines after prolonged use. To maintain a constant material removal efficiency, a pad conditioner is used to unglaze (i.e., condition) the polishing pad.
During wafer planarization, certain issues arise including microscratching (i.e., micrometer scale scratches), under or over-polishing, and dishing. Main contributors to microscratching include abrasive particles from the slurry, loose materials from polishing, loose diamonds from pad conditioners, and metal particles from the pad conditioner.
In addition to microscratching, some metals such as, for example, nickel may pose a contamination issue. For example, embedded nickel particles in the wafer surface may result in shifts in electrical or reliability performance of active/passive devices and interconnects. For example, the electrical performance of a metal-oxide-semiconductor field-effect transistor (MOSFET) can be adversely affected by nickel contamination. Also, copper interconnects can become electrical short circuited when nickel contamination causes electrical bridging between separate copper traces.